The present invention generally pertains to rotary lawn mowers. A rotary mower may be generally defined as a mowing implement with a cutting blade mounted for rotation about a substantially vertical axis to define a generally horizontal rotary cutting path.
There are at least three different ways to handle the grass clippings created by a rotary lawn mower. The clippings can be bagged; simply thrown on top of the lawn using a side discharge chute or chute extension; or "mulched." As the present invention pertains particularly to a convertible rotary lawn mower which can selectively bag, throw or mulch grass clippings, all three approaches will be described briefly below.
As noted above, one way to deal with grass clippings produced by a rotary lawn mower is simply to scatter the grass clippings over the top surface of the cut lawn. This is normally accomplished by using a side discharge mower or rear bagger with a side discharge chute extension. Although this approach is quick and easy, if a highly groomed lawn is desired it is generally thought that this particular approach is not optimum. The layer of grass clippings lying atop the lawn tends to yellow and detract from the lush, green appearance normally associated with a healthy lawn. What's more, the layer of grass clippings can prevent the free transport of water and sunlight to the growing grass blades and the decomposing grass clippings cannot efficiently return nutrients to the soil. However, there are indeed situations when a side discharge approach is highly desirable. For example, if the grass is extremely long and the appearance of the lawn is not of paramount importance, side discharging might be the best approach.
Given the fact that simply scattering the grass clippings in a layer atop the lawn is sometimes undesirable, bagging and mulching are often considered advantageous. Collecting the grass clippings in a grass bag is important if one wants to achieve a formal, "groomed" appearance and if one wishes to prevent grass clippings from being tracked into the house. Using a grass bag is sometimes desirable from a safety standpoint, as well, as it can reduce the risk of thrown objects.
Although bagging grass clippings has the advantages described briefly above, it also has some disadvantages which make it less than desirable in certain circumstances. For example, it can be very time consuming to empty a grass bag every time it fills. If long, lush grass is being mowed, it may be required to empty the grass bag every five or ten minutes or so, thus possibly doubling the time it takes to mow the lawn. Also, there is the issue of what to do with the grass clippings once they are collected. In the past, the grass clippings could simply be set out with the other household trash. Recently, however, many municipalities have started to charge additional fees for handling grass clippings, and some are even requiring the homeowner to take the grass clippings to a central deposit on his or her own. Particularly in the spring and early summer, grass clippings can make up a fairly large percentage of the solid waste being deposited in land fills. Thus, from a variety of standpoints it may be desirable to reduce "bagged" grass clippings. This must be balanced against the desire of many homeowners to have a very "formal" looking lawn substantially devoid of grass clippings. Bagging is unquestionably desirable when cutting very lush, long and/or damp grass, at least from the standpoint of aesthetics, but there are times when bagging is simply unnecessary, and side discharging or mulching might be adequate.
Mulching is the third general way to handle grass clippings. In mulching it is desirable to cut the clippings to as short a length as possible to ensure that the clippings are small enough to be driven beneath the surface of the standing grass blades, down to the soil. It is also desirable to violently agitate the grass as it is being cut to again facilitate deposit of the clippings below the lawn surface. Mulching of grass clippings clearly possesses several advantages. For example, it is much faster and easier to mow a lawn when the grass is not being bagged. The lawn mower is much lighter and it is unnecessary to stop every five minutes to one-half hour to empty the bag. Also, since no grass clippings are collected, the homeowner does not have to worry about solid waste disposal charges or responsibilities. Mulching minimizes thrown object risks as well: most mulching mowers do not have a discharge chute through which to throw rocks, etc.
However, there may be times when mulching is undesirable. For example, if the grass is quite long, lush and/or damp, it may be desirable to bag or side discharge the grass to avoid grass clumping, an effect which to some degree is unavoidable when using even efficient mulching mowers. Thus, it may be desirable to bag or side discharge the grass clippings in the spring and early summer, but mulch the rest of the year, or perhaps to bag when the grass is medium length, side discharge when the grass is extremely long, but mulch otherwise. Or, it might be appropriate to bag the clippings regardless of the length of the lawn to minimize the dissemination of weed seeds if the lawn harbors various broad leaf weeds, for example.
Therefore, it is clear that there are times when it would be very desirable to bag grass clippings and times when it would perhaps make more sense to mulch or side discharge the grass clippings, depending on weather conditions, local rules and regulations concerning grass clippings, time between mowings, and grass conditions, among other things. However, prior art mowers, whether baggers, side dischargers or mulchers, cannot easily be converted from one mode of mowing to another. Manufacturers have certainly offered bagging mowers that have discharge chute doors which can be closed to theoretically convert the mower to a mulcher, but such mowers tend to clog in the mulching mode and generally do not do a very good job of mulching.
One common type of mulching mower includes a deep deck housing, without a discharge chute, and a special mulching blade which has a longer than normal cutting edge and a severely stepped or offset configuration which are presumably provided to allow the cutting blade to repeatedly impact and cut the grass clippings to render them small enough to penetrate the surface of the standing grass. Since "dedicated" mulching mowers of this type do not include a chute, they obviously cannot be used to bag the grass clippings irrespective of weather conditions, length, lushness or dampness of the grass, etc.
As noted above, another type of "mulching mower" is a standard bagging mower having a spring-loaded door for selectively blocking the discharge chute. When the door is open the grass bag is mounted to the mower. When the grass bag is removed the door automatically closes and, in theory, the lawn mower can be used to mulch. While in principle this would seem to be a very logical way to bag or mulch, on demand, it turns out that the housings of most bagging lawn mowers are not designed to accommodate mulching. Instead, they are designed to entrain a large amount of air to transport the clippings through a discharge chute and into the grass bag. When the standard bagging lawn mower is attempted to be used as a mulcher, the blade and housing actually create too much air flow and tend to flatten the grass blades rather than cut and mulch them. And, such mowers tend to clog, causing the clippings to fall from the housing in clumps.
It has been discovered that guide vanes or "kickers" mounted in the mower cutting chamber can greatly improve mulching performance. The kickers, guide vanes or baffles mounted within the cutting chamber essentially disrupt the stream of grass clippings suspended therein and direct the clippings generally downwardly and/or inwardly into the cut path. The kickers in combination with proper housing and blade design provide excellent clipping dispersion under varying lawn conditions. One type of mulching mower with kickers, shoWn and described in U.S. Pat. No. 4,205,512, assigned to the assignee herein, was offered by The Toro Company in the late 70's and early 80's. The Toro walk-behind mulching mower was a "dedicated" mulcher as it did not include a discharge chute and was not capable of bagging the grass clippings. Toro also offered a mulching kit for a riding lawn mower which included a discharge chute cover and a plurality of kickers which could be mounted within the cutting chamber, but in order to convert the lawn mower from a non-mulcher to a mulcher, many steps were required, including detaching the deck from the traction vehicle, securing the discharge chute cover with fasteners, removing a baffle mounted in the housing, and attaching the "kickers." To convert from a mulcher to a non-mulcher the steps had to be reversed.
Another manufacturer offers a "Mulcherizer Kit" for its walk-behind rotary lawn mowers. Reference is made to U.S. Pat. No. 4,189.903, which discloses this kit. It includes a plastic liner having roughly the same shape as a lawn mower housing having integrally molded guide vanes or kickers. The liner attaches to the underside of the housing and blocks the discharge chute, thus converting the lawn mower into a mulcher. A special mulching blade is also used in lieu of the standard bagging blade. To return to the bagging mode, the mulching blade and liner are removed, and the standard bagging blade is reconnected. Obviously, the Mulcherizer Kit of the '903 patent does not allow the operator to easily convert from bagging to mulching and vice versa.
The present invention addresses the problems discussed above. Specifically, the present invention is directed to a convertible lawn mower which can be easily converted from a bagger to a mulcher and vice versa, depending on weather conditions, grass conditions, and other factors.